diff --git a/crates/provider/src/common.rs b/crates/provider/src/common.rs
index dad2d4e2d..da248e1f7 100644
--- a/crates/provider/src/common.rs
+++ b/crates/provider/src/common.rs
@@ -250,7 +250,7 @@ impl MwdForTime {
     #[cfg(any(feature = "tzif", feature = "experimental_tzif"))]
     pub(crate) fn from_seconds(seconds: i64) -> Self {
         let (year, month, day_of_month) = utils::ymd_from_epoch_milliseconds(seconds * 1_000);
-        let week_of_month = day_of_month / 7 + 1;
+        let week_of_month = (day_of_month - 1) / 7 + 1;
         let day_of_week = utils::epoch_seconds_to_day_of_week(seconds);
         let mut mwd = Mwd::from_u8(month, week_of_month, day_of_week);
         let days_in_month = utils::iso_days_in_month(year, month);
diff --git a/crates/temporal/src/builtins/compiled/plain_date_time.rs b/crates/temporal/src/builtins/compiled/plain_date_time.rs
index c9d2675ef..8f745b1ae 100644
--- a/crates/temporal/src/builtins/compiled/plain_date_time.rs
+++ b/crates/temporal/src/builtins/compiled/plain_date_time.rs
@@ -44,4 +44,25 @@ mod tests {
         // Should disambiguate to 2020-03-08T01:30:00-08:00[America/Los_Angeles]
         assert_eq!(zdt.hour(), 3);
     }
+
+    #[cfg(feature = "tzdb")]
+    #[test]
+    fn new_york_standard_time_before_dst_start() {
+        use crate::{options::Disambiguation, tzdb::CompiledTzdbProvider, PlainDateTime, TimeZone};
+        let provider = &CompiledTzdbProvider::default();
+
+        // DST starts on 2026-03-08, so 2026-03-07 is still standard time.
+        let pdt = PlainDateTime::try_new_iso(2026, 3, 7, 12, 0, 0, 0, 0, 0).unwrap();
+        let zdt = pdt
+            .to_zoned_date_time_with_provider(
+                TimeZone::try_from_identifier_str_with_provider("America/New_York", provider)
+                    .unwrap(),
+                Disambiguation::Compatible,
+                provider,
+            )
+            .unwrap();
+
+        assert_eq!(zdt.hour(), 12);
+        assert_eq!(zdt.offset(), "-05:00");
+    }
 }